Differences
This shows you the differences between two versions of the page.
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fss:sessions:session4-android [2019/07/11 16:19] beniamin.dobre [Threading in Android] |
fss:sessions:session4-android [2019/07/11 18:36] (current) beniamin.dobre [Handlers and Runnables] |
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| - | ====== Android Session 3: Bluetooth Low Energy Communication ====== | + | ====== Android Session 4: Data Management ====== |
| - | {{:fss:sessions:android_bluetooth_low_energy_communication.pdf|Slides}} | + | {{:fss:sessions:android__data_management.pdf|Slides}} |
| ===== Objectives ===== | ===== Objectives ===== | ||
| * Store data using SharedPreferences | * Store data using SharedPreferences | ||
| * Build and interact with databases in Android | * Build and interact with databases in Android | ||
| + | |||
| + | ==== Shared preferences ==== | ||
| + | The Android framework offers an API for storing key-value pairs accessible only to your app. Usually they are used for persisting settings (user preferences). | ||
| + | |||
| + | The key-value pairs are stored in files. You can use one or several files, depending on your app's design. In order to access them, you need to obtain a SharedPreference object using methods provided by the Context class. These files can also be specific to an activity. | ||
| + | <code Java> | ||
| + | // In this example we are in MainActivity | ||
| + | |||
| + | SharedPreferences sharedPref = this.getPreferences(MODE_PRIVATE); | ||
| + | // or | ||
| + | sharedPref = this.getSharedPreferences("mysettings", Context.MODE_PRIVATE); | ||
| + | // or | ||
| + | sharedPref = PreferenceManager.getDefaultSharedPreferences(context); | ||
| + | </code> | ||
| + | |||
| + | |||
| + | *[[https://developer.android.com/reference/android/content/Context.html#getSharedPreferences(java.lang.String,%20int)|Context.getSharedPreferences]] is used when we have multiple shared preferences files and we want to obtain the given name | ||
| + | * [[https://developer.android.com/reference/android/app/Activity.html#getPreferences(int)|Context.getPreferences]] if we only use one shared preference file for that activity. We can only provide the MODE_PRIVATE since the other options have been deprecated from API Level 17 for security reasons. They granted read and write access to these files to other apps. | ||
| + | * [[https://developer.android.com/reference/android/preference/PreferenceManager.html#getDefaultSharedPreferences(android.content.Context)|PreferenceManager.getDeaultSharedPreferences]] provides the default file for storing the key-value pairs for the entire app. | ||
| + | |||
| + | <code Java> | ||
| + | SharedPreferences.Editor editor = getPreferences(MODE_PRIVATE).edit(); | ||
| + | editor.putString("my_key", "my_value"); | ||
| + | editor.putBoolean("my_bool", true); | ||
| + | editor.putInt("my_int", 0); | ||
| + | |||
| + | // Must save them! | ||
| + | editor.apply(); //async write to disc | ||
| + | // or use | ||
| + | editor.commit(); //immediately writes to disc, avoid using it from UI thread. | ||
| + | |||
| + | //obtain values: | ||
| + | sharedPref.getString("my-key", "default-value"); | ||
| + | </code> | ||
| ==== Threading in Android ==== | ==== Threading in Android ==== | ||
| Line 65: | Line 99: | ||
| HandlerThread thread = new HandlerThread("I handle things"); | HandlerThread thread = new HandlerThread("I handle things"); | ||
| thread.start(); | thread.start(); | ||
| - | writeHandler = new Handler(thread.getLooper()); | + | Handler writeHandler = new Handler(thread.getLooper()); |
| writeHandler.postDelayed(new Runnable() { | writeHandler.postDelayed(new Runnable() { | ||
| Line 80: | Line 114: | ||
| - | ==== TASK ==== | + | ==== TASKS ==== |
| - Setup SharedPreferences (Follow TODO 1) | - Setup SharedPreferences (Follow TODO 1) | ||
| - Get sharedPreferences | - Get sharedPreferences | ||
| Line 93: | Line 127: | ||
| - Load data on a different thread (not on the UI thread) | - Load data on a different thread (not on the UI thread) | ||
| - Set the list of records to the adapter on the UI thread | - Set the list of records to the adapter on the UI thread | ||
| + | |||
| + | ===== Files ===== | ||
| + | {{:fss:sessions:android_4_start.zip|}} | ||
